In recent years, in an outdoor unit for an air-conditioning apparatus installed at a building, a commercial facility, or other similar structure, heat exchangers are disposed at the back side and the right and left sides of the outdoor unit. A fan is installed at an upper portion of the outdoor unit. A negative pressure is produced in the outdoor unit by driving the fan, so that the ambient air around the outdoor unit is sucked into the outdoor unit, and heat is exchanged between the air and refrigerant in the heat exchangers.
Each heat exchanger is configured such that heat-transfer pipes penetrate fins in a direction perpendicular to the fins. Each heat-transfer pipe is, for example, a circular pipe, and the fins reject heat transmitted from the circular pipe by the refrigerant moving in the circular pipe. Here, each heat-transfer pipe is described as a circular pipe, but may be, for example, a flattened pipe having a flattened shape.
In the related art, an outdoor unit for an air-conditioning apparatus having a structure in which, in the case where a plurality of heat exchangers are provided, the number of rows of heat-transfer pipes of the heat exchangers is increased by stacking the heat exchangers in the height direction, has been proposed (see, for example, Patent Literature 1). In the plurality of heat exchangers stacked in the height direction, a sheet metal for preventing the heat exchanger at the upper side from falling downward is disposed at an upper portion of the heat exchanger at the lower side. The heat exchanger at the lower side supports and fixes the heat exchanger at the upper side using the sheet metal.
In the heat exchangers disclosed in Patent Literature 1, a bottom plate for supporting a lower end portion of the heat exchanger provided at the lower side is disposed. However, dew condensation water (drain water) generated from the heat exchangers remains on the bottom plate, and thus the fins and the heat-transfer pipes of the heat exchangers may be frozen or corroded by the dew condensation water.
Consequently, an outdoor unit for an air-conditioning apparatus has been proposed in which a plurality of drain water outlets are provided in a bottom plate of the outdoor unit, dew condensation water generated at a heat exchanger is drained through the drain water outlets to prevent freezing and corrosion of fins and heat-transfer pipes of the heat exchanger (see, for example, Patent Literature 2).
In an existing outdoor unit for an air-conditioning apparatus, a slope is provided to a bottom plate of the outdoor unit, and a drain water outlet is provided at the downstream side of the slope so that dew condensation water remaining on the bottom plate is drained through the drain water outlet by using the slope.
For example, an outdoor unit for an air-conditioning apparatus has also been proposed in which a plurality of louver-like cut-and-raised parts are provided on a bottom plate of the outdoor unit for an air-conditioning apparatus at a position at which a heat exchanger is placed so that the strength of the bottom plate is enhanced while the efficiency of draining dew condensation water generated at the heat exchanger is improved (see, for example, Patent Literature 3).
Furthermore, an outdoor unit for an air-conditioning apparatus has been proposed in which heat pipes are disposed at the lowermost stage of a heat exchanger provided in the outdoor unit for an air-conditioning apparatus so that dew condensation water generated at the heat exchanger is heated to avoid freezing of the dew condensation water (see, for example, Patent Literature 4).